This study tested D. M. Clark and A. Wells’ (1995) proposition that negative post-event rumination is produced by negative self perceptions formed by socially phobic individuals during anxiety-provoking events. A socially phobic group and a nonanxious control group performed an impromptu speech, and appraised their performance immediately afterwards. One week later, participants were assessed as to how frequently they had had negative thoughts about the speech, how much they engaged with these thoughts, how distressing these thoughts were, and how much control they felt they had over the thoughts. The socially phobic group engaged in more negative rumination than controls on each of these levels, and perceived their performance as worse than controls immediately after the speech. Perception of performance was found to mediate the relationship between social anxiety and post-event rumination, providing support for Clark and Wells’ model.